I'm having problems with both my speedometer and teleflex through hull digital depth finder. The speedometer only seems to work at speeds above 20 mph, and the depth finder doesn't work at all. I opened up my dash last night and noticed there is a very small black and red wire that connect to the speedometer. The wires are actually connected to a small round black plastic peice, which is inserted into a hole on the back of the speedo and taped in place. Any ideas?